1. Field of the Invention
The present invention relates generally to protective layers fabricated upon magnetic layers of hard disk media, and more particularly to thin film diamond-like carbon protective layers.
2. Description of the Prior Art
Standard magnetic media hard disks include a magnetic layer that is covered by a protective overcoat layer. The overcoat layer is necessary to provide both mechanical and corrosion protection for the magnetic layer, and typical prior art overcoat layers are composed of a hard, carbon based composition that is applied by a magnetron sputtering technique to a thickness of approximately 50 to 200 Å.
The ongoing efforts to increase the areal data storage density of magnetic disks have resulted in a need to reduce the thickness of the overcoat layer while increasing the hardness, or density of the overcoat layer. It has been found that a typical magnetron sputtered overcoat of below approximately 50 Å is not sufficiently hard, nor does it provide sufficient corrosion protection to the magnetic layer, due to the generally low energy (approximately 10 eV) at which the carbon atoms are deposited. Efforts to create a thin, hard, corrosion resistant overcoat have therefore been directed towards fabrication devices such as mass selected ion beam deposition (MSIB), cathodic arc, laser plasma deposition and plasma enhanced chemical vapor deposition (PECVD) which produce carbon atom deposition energies of 100 eV or more. While such 100 eV deposited overcoat layers provide good mechanical and corrosion resistance properties, they also create deterioration problems for the underlying magnetic layer. Specifically, at such high energies, the carbon atoms, as well as other atoms such as nitrogen and hydrogen that are often utilized in forming the overcoat layer, become implanted into the magnetic layer to a significant depth. The implanted atoms can seriously degrade the magnetic properties of the magnetic layer within its upper regions, thus resulting in degraded performance of a magnetic disk that is fabricated with an overcoat layer formed with prior art high energy carbon deposition techniques.
The present invention solves these prior art problems through the use of an energy gradient ion beam deposition technique in which the implanting of carbon overcoat ions into the magnetic layer is reduced.